In our PCT patent application WO 95/13531 we describe reading devices for assay devices utilising test strips. Typically the assay device comprises an elongate casing containing the test strip and having in the casing one or more “windows” through which an assay result region or zone of the test strip can be observed. The preferred reading device includes a slotted receiving portion into which the assay device can be inserted and wherein the assay result is determined by electromagnetic means, particularly the transmission of light through the test strip. For accurate determination of the assay result the detection zone of the test strip must be correctly located within the reading device relative to the light path or other features that make up the result reading system. WO 95/13531 describes various ways in which the correct receipt of the assay device within the reading device can be facilitated.
A primary objective of these test kits is that they should be usable by untrained persons and especially by the consumer in the home. When the ordinary consumer is invited to use any apparatus which requires physical engagement of one unit with another, it can be surprisingly common for this action to be performed incorrectly. Carefully worded and illustrated instructions provided by the manufacturer may be mis-interpreted, or often are ignored altogether. In the present context, where the accurate reading of a sensitive assay result is required, it is essential that precise placement of the assay device within the reading device is achieved. Any mis-alignment or incorrect engagement of these two units can lead to an inaccurate or mis-leading assay reading. This problem is particularly acute where the reading system does not include any facility to scan the assay device to locate the appropriate portion that should be read. The cost and complexity of the reading system can be substantially reduced if the precise location of the detection zone within the assay device is controlled during manufacture and the device is presented to the reading device in a constant manner so that the detection zone is always in the same position relative to the reading system. It is an objective of the invention to provide a test kit in which the likelihood of user error during presentation of the assay device to the reading device is substantially reduced. An associated objective is to provide a test kit in which reading of the assay device is not initiated unless the assay device has indeed been correctly presented to the reader, or in which the user is alerted to the mis-presentation of the assay device. In WO 95/13531 we describe some mechanisms to facilitate accurate placement, but the present invention provides further improvements.
The invention will be described with particular reference to test kits useful in monitoring of body fluid analytes, and especially to home monitoring of urinary analytes of relevance to the determination of the status of the human ovulation cycle. This is by way of example only, and it will be appreciated that the invention is useful in many other contexts where other sample liquids and analytes are involved. Examples of other types of analyses, in which accurate assay results are desirable and where a kit in accordance with the invention may be appropriate include assays for cancer markers, cardiac markers, blood glucose, drugs of abuse, hormones, infectious disease markers, tests in therapeutic drug monitoring, manufacturing and raw material quality control, and tests for effluent and pollution levels.